Note: Descriptions are shown in the official language in which they were submitted.
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TITLE
[0001] Primer for Composite Building Materials
BACKGROUND
[0002] This invention relates generally to primers, and in particular, to
improved primers for
building materials.
[0003] Primers, particularly those for building materials must be engineered
to integrate with
the building material itself and endure conditions subjected to the building
material. Typical
conditions that negatively impact many building materials are temperature
changes, water
absorption, soluble salt ingress, efflorescence, and stacking, to name a few.
Unfortunately,
most primers when applied to a composite building material, including those
comprising a
cementitious substrate, do not effectively reduce water absorption, salt
accumulation, and
effloresce and do not allow the building material to endure stacking. It is
difficult to find a
primer that can protect against all such conditions; no conunercial primer is
capable of such
enhanced performance nor is any capable of integrating well with composite
materials.
SUMMARY
[0004] As described herein is a primer with improved properties for composite
building
materials, such as a cementitious material, gypsum, or other inorganic
composite material. The
improvements include resistance to water ingress, soluble salt ingress,
weather, efflorescence
and stacking dama.ge. Consequently, a paint or topcoat applied to the primer
will exhibit
improved service life. The described primer is capable of maintaining durable
contact between
the substrate: the sealer and any exterior coating (e.g., paint).
[0005] The irnproved formulation effectively blocks moisture from penetrating
the composite
building material and is better than commercial primers. The formulation also
improves
adhesion and prevents peel failure of a topcoat when applied to the composite
building
material. The improved formulation acts as a weather-guard and a hydrophobic
treatment to
all surfaces of the composite building material upon application.
[0006] Some embodiments provide a primer suitable for use on a fiber cement
substrate.
The primer offers superior blocking resistance and wet adhesion. In addition,
the primer
exhibits salt resistance in a freeze-thaw environment for superior protection
of a composite
building material.
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[0007] A primer formulation described herein comprises resins that include one
or more
polymers or copolymers of an acrylic, styrenated acrylic, acrylic
polyurethane, acrylic epoxy,
epoxy ester, polyester, alkyd, amino resin or any combination blend. The
polymers or
copolymers may be thermoplastic or thermosetting systems. The primer
formulation further
comprises up to 60% water, up to 1% of one or more dispersants, up to 0.5% of
one or more
wetting agents, up to 1% of one or more biocides, up to 1% of one or more
antiblocking
agents, up to 0.5% of one or more thickeners, up to 1% of one or more pH
adjusters, up to
50% of one or more resins, up to 30% of one or more pigments, up to 70% of one
or more
extenders or fillers and up to 1% of one or more functional pigments. In some
embodiments,
the resin is an acrylate polymer. The acrylate polymer may be latex. The one
or more
dispersant may be a hydrophobic copolymer polyelectrolyte. The one or more
wetting agents
may be an acrylic wetting agent. The one or more biocides may be an industrial
alginate. The
one or more thickeners may be a non-ionic urethane. The one or more pigments
may be
titanium dioxide or iron oxide or phthalocyanine blue or combinations thereof.
The one or
more extenders may be calcium carbonate, talc, calcined clay, calcium silicate
and/or
combinations thereof.
[0008] In some embodiments a primer comprises a polymer wherein the polymer
has a glass
transition temperature (Tg) of about 50 to 70 C and a minimum film formation
temperature of
about or below 30 C.
[0009] Some embodiments further provide a primer that comprises at least one
hard polymer
and at least one soft polymer wherein the hard polymer has a Tg of about 30 C
or less and the
soft polyrner has a Tg of about 50 C or greater.
[0010] Still further embodiments provide a primer that comprises one or more
polymers
where in the polymer particle size distribution is bimodal. The bimodal
particle size
distribution may have a first peak at or below 100 nanometers and a second
peak at or greater
than 200 nanometers.
[0011] Those skilled in the art will further appreciate the above-noted
features and
advantages of the invention together with other important aspects thereof upon
reading the
detailed description that follows and in conjunction with the drawings
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BRIEF DESCRIPTION OF THE DRAWINGS
[0012] For more complete understanding of the features and advantages of the
inventions
described herein, reference is now made to a description of the invention
along with
accompanying figures, wherein:
[0013] FIG. 1 is a representative photograph of cross-sections of impregnated
building
material samples after wet picking of a formulation described herein as
compared with a
commercially available primer, wherein the photograph shows two wet pickings
as marked by
the left two rectangular-shaped regions;
[0014] FIG. 2 is a representative photograph of cross-sections of impregnated
building
material samples after stacking comparing stacking resistance of a formulation
described herein
as compared with a commercially available primer;
[0015] FIGS. 3A-C are representative photographs of fiber cement specimen
after 40 cycles
of salt freeze-thaw, wherein FIGS. 3A-3B are specimens coated with an
alternative
conventional primer and FIG. 3C is a specimen coated with a representative
primer forrnulation
described herein; and
[0016] FIG. 4 depicts efflorescence of specimens coated with a sealer and
paint formulation
described herein, wherein FIGS. 4A-4B are specimens coated with representative
primer
forinulations described herein and FIG. 4C is a specimen coated with an
alternative
conventional primer.
DETAILED DESCRIPTION
[0017] Although making and using various embodiments are discussed in detail
below, it
should be appreciated that the description provides many inventive concepts
that may be
embodied in a wide variety of contexts. The specific aspects and embodiments
discussed
herein are merely illustrative of ways to make and use the invention, and do
not limit the scope
of the invention.
[0018] References will now be made to the drawings wherein like numerals refer
to like or
similar parts throughout. The drawing figures are not necessarily to scale and
certain features
may be shown exaggerated in scale or in somewhat generalized or schematic form
in the
interest of clarity and conciseness.
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[0019] As further described herein, wet adhesion was evaluated using a
modified ASTM
D3359, which differed in that samples did not receive an X cut and cross cut.
The adhesive
was a 1 inch wide adhesive of 3M Scotch tape No. 250 applied directly to a
coated surface
(e.g., primed and/or painted) after the surface (typically the entire sample)
was soaked in tap
water for about 24 hours. The top surface of the tape was rolled with a 10 lb.
rubber roller at
for 10 cycles to promote adhesion. Tape was then removed at a 90 degree angle.
[0020] Freeze-thaw assessment was in accordance with ISO-DP8336 Standard Test
Method
with some modification to sample preparation. Water absorption was modified
from ASTM
D570 Standard Test Methods for Water Absorption of Plastics. Efflorescence
evaluation
relied on a modified ASTM C67.07 Standard Test Methods for Sampling and
Testing Brick
and Clay Structural Tile. For QUV assessment, ASTM G53 was used as a source
for
assessment.
[0021] Few primers integrate well with composite building materials. For
example, there are
only a few primers that are prepared for integration with cementitious
substrates. Commercial
primers, however, do not achieve a balanced performance between blocking and
wet adhesion.
As depicted in TABLE 1, different conventional primers (C-1, C-2 C-3). are
poor at either
blocking or wet adhesion when applied to a composite building material. Based
on such data,
these primers could not be used in production to coat a surface of a composite
building
material, such as a cementitious product. Such conventional primers were
compared with a
formulation described herein (DC-001) also applied to the same type of
composite building
material. DC-001 was found to be more effective than the conventional primers
at both
blocking and wet adhesion. Blocking, as referred to herein, describes a non-
sticking
performance of the coating after building materials are coated with a primer
are stacked one on
top of another.
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TABLE 1. Blocking and wet adhesion of primers.
Blocking Resistance Wet Adhesion
C-1 2(5)1 5%
C-2 2(5)1 90%
C-3 1(1) 70%
DC-001 1(2) 0.5%
[0022] With TABLE 1, specimens used were sample boards of fiber cement
material with
the following dimension: 3 foot x 81/4 inch x 1/4 inch. To each specimen, a
textured surface was
applied to one surface (face) of each specimen. Surfaces were then sealed,
applied with a
primer and then cured. Specimens were contacted in a face-to-face (texture-to-
texture)
configuration after surface temperatures of the specimens reached a
temperature of about 125
F. Values in parenthesis are associated with picking damage, as described
further below.
[0023] For blocking, a modified ASTM D2793 was used in which specimens were
stacked
and pressed at about 70 pounds per square inch (psi) at 125 Fahrenheit for
about 5 minutes.
A pressure of 70 psi is similar to a typical weight of about 10 pallets of
composite building
materials stacked together. The elevated temperature is representative of a
surface
temperature that such a material may reach when stacked. When blocking, a
value of 1 (e.g.,
TABLE 1, before parenthesis) indicates boards are easily separated (no
blocking). A value of
2 indicates some type of blocking (boards stick to each other and do note
easily separate). The
number in parenthesis represents the surface dama.ge as a percentage. For
TABLE 1, the letter
code after the parenthesis indicates the force required to separate specimens:
s for minor
force; m for moderate force; l for large force.
[0024) For wet adhesion, specimens were prepared as described for blocking
with the same
layers: a sealer followed by a primer. After application of a sealer and
primer, two coats of the
same topcoat were applied for all specimens. Application of each layer
(sealer, primer,
topcoatl, topcoat2) was followed by drying at an elevated temperature (baking)
after which
specimens were allowed to dry, cool and set for one to three days.
Subsequently, specimens
were soaked for 24 hours in tap water. Each specimen was weighed before and
after soaking
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in water. Paper towels were used to remove the water from the surface of each
sample after
soaking. 3M Scotch tape No. 250 was then applied to a surface of the
specimen, rolled with
a 10 pound roller and then removed quickly.
[0025] Referring back to TABLE 1, the table shows that 70% of a conventional
primer (C-
3) had peeled off with removal of tape (wet adhesion evaluation) while the
primer did not
experience blocking problems. On the other hand, another conventional primer
(C-1) did
exhibit a blocking problem, although the primer adhered relatively well after
removal of tape
when evaluated for wet adhesion. Neither C-1 nor C-3 would be adequate primers
for a
composite building material such as a cementitious substrate. Certainly C-2,
which was very
poor at both blocking and wet adhesion, would not be a suitable primer for a
composite
substrate, such as a cementitious material. The data for C-1, C-2 and C-3 are
compared with
that for DC-001, which generally shows no loss of paint with wet adhesion
evaluation and no
blocking problems. TABLE 1 proves that a formulation described herein achieves
a desired
balance between blocking and wet adhesion.
[0026] Representative examples of several specimens after wet adhesion or
blocking
resistance are depicted in FIG. 1 and FIG. 2, respectively. As shown in the
figures, only the
primer formulation described herein, represented by DC-001, exhibited both
good wet
adhesion (FIG. 1) and resistance to blocking (FIG. 2).
[0027] Each specimen as used herein is a representative building material,
which is typically
a porous material comprising one or more different materials such as a gypsum
composite,
cement composite, geopolymer composite or other composites having an inorganic
binder.
The surface of the material may be sanded, machined, extruded, molded or
otherwise formed
into any desired shape by various processes known in the art. The building
material may be
fully cured, partially cured or in the uncured "green" state. The building
material may further
include gypsum boards, fiber cement boards, fiber cement boards reinforced by
a mesh or
continuous fibers, gypsum boards reinforced by short fibers, a mesh or
continuous fibers,
inorganic bonded wood and fiber composite materials, geopolymer bonded wood
and fiber
boards, concrete roofing tile material, and fiber-plastic composite materials.
Preferred fibers
include various forms of cellulose fibers, such as treated or untreated,
bleached or unbleached
Kraft pulp. Other forms of fibers may be used. Suitable examples are those
from ceramic,
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glass, mineral wool, steel, and synthetic polymers (e.g., polyamides,
polyester, polypropylene,
polymethylpentene, polyacrylonitrile, polyacrylamide, viscose, nylon, PVC,
PVA, rayon, glass
ceramic, carbon, any mixtures thereof).
[0028] Any additional additive may be optionally incorporated into a composite
material
including but not limited to density modifiers, dispersing agents, silica
fume, geothermal silica,
fire retardant, viscosity modifiers, thickeners, pigments, colorants,
dispersants, foaming
agents, flocculating agents, water- proofing agents, organic density
modifiers, aluminum
powder, kaolin, alumina trihydrate, mica, metakaolin, calcium carbonate,
wollastonite,
polymeric resin emulsions, hydrophobic agents, and mixtures thereof.
[0029] To determine water resistance of primers described herein, water
absorption was
evaluated by coating building material specimens on all sides with one coat of
primer. A
representative example of water absorption analyses is shown in TABLE 2
comparing
conventional primers (C-2, C-3, C-4) with a primer formulation described
herein (DC-001).
Building material specimens were fiber cement substrates cut to a size of
approximately 4 feet
x 4 inches x'/4 inch. All primers were directly applied to a surface of each
specimen with a
defined dry film thickness (DFT) in process line. Subsequently, specimens were
soaked for up
to 24 hours (hrs) in tap water. Each specimens was weighed before and after
soaking in water.
Paper towels were used to remove the water from the surface of each sample
after soaking.
Water absorption was calculated as [(weight after soaking - weight before
soaking)/(weight
before soaking)] x 100. Overall, representative primer, DC-001, showed very
good water
resistance performance as compared with alternative conventional primers (C-2,
C-3, C-4).
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TABLE 2. Water absorption in tap water.
Water absorption (wt.%)
0 hrs 2 hrs 4 hrs 8 hrs 24 hrs
C-2 0 20.83 25.81 28.35 28.37
C-3 0 20.56 24.68 27.28 27.33
C-4 0 14.60 20.71 26.26 28.29
DC-001 0 3.65 6.44 11.28 26.29
[0030] A similar procedure as described for tap water absorption was followed
for salt water
absorption. The solution used was 3.5 wt.% sodium chloride in distilled water.
Only a single
coat of primer was applied to each specimen. TABLE 3 illustrates the salt
water absorption
of a representative primer formulation (DC-001) as compared with conventional
primers, C-2,
C-3 and C-4 in a 3.5% salt water solution. After eight hours of soaking,
specimens coated
with a conventional primer had salt water absorption of around 27% while DC-
001 had less
than 18% salt water absorption. Thus, DC-001 significantly blocked salt water
from entering
the specimens.
TABLE 3. Absorption of salt water.
wt.%
2 hrs 4 hrs 8 hrs 24 hrs
C-2 21.45 26.37 28.90 29.10
C-3 20.39 24.13 26.98 27.69
C-4 17.2 23.9 27.68 29.03
DC-001 4.86 9.07 17.51 28.51
[0031] Primer formulation DC-001 was further examined in salt-freeze thaw
cycles against
conventional primer samples, C-3 and C-4. The freeze-thaw test used
temperatures of -20
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degrees Centigrade to +20 degrees Centigrade. Specimen of fiber cement were
coated with a
single layer of one of the primers with no additional coating. Specimens were
then exposed to
40 salt freeze-thaw cycles. FIG. 3 shows representative specimens after 40
salt freeze-thaw
cycles. There was damage and loss of primer on the surface of specimens
coating with C-3 or
C-4 primers; on the other hand, primer DC-001 remained in good condition.
[0032] QUV weathering was performed in an accelerated weathering chamber
equipped with
QUV-SE ultraviolet (UV)-B bulbs allowing a flexible mix of UV light,
temperature and
moisture conditions. The chamber is used to accelerate damage caused by
sunlight, rain, and
condensed surface moisture or dew. Primed specimens were subjected to
alternating cycles of
light and moisture at controlled elevated temperatures. The selected
conditions were
continued for up to 1000 hours. Each sample was coated with one of the primers
identified in
TABLE 4.
[0033] One important goal of coatings for building materials is sunlight
durability, which is
commonly measured by evaluating change in gloss and color relative to the
amount of sunlight
striking the surface. QUV weathering using UVB bulbs is one such measurement
for sunlight
durability because it accelerates sun exposure. Changes in gloss of a surface
after QUV
weathering indicate either polymer film or pigment breakdown or both.
Likewise, pigment
change and polymer breakdown are represented by a change (0) in light to dark
(L) and yellow
to blue (b), respectively.
[0034] To compare weather resistance of conventional primers and
representative
formulations described herein, C-4 (conventional primer) and DC-00l and DC-002
(representative primer formulations) were exposed to QW weathering for up to
1000 hours.
Primers were coated directly onto raw fiber cement boards. TABLE 4 shows data
for AL and
Ab. Color shifts after 1000 hours were observed with C-4, while little changes
occurred with
DC-001 and DC-002.
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TABLE 4. QUV.
QUV time Color data C-4 DC-001 DC-002
AL 0.18 0.21 0.1
141 hrs
Ob 0.24 -0.03 -0.09
AL 0.13 0.26 0.09
409 hrs
Ab 0.91 -0.03 -0.08
AL 1.24 0.25 0.27
1003 hrs
Ob -0.66 -0.07 -0.23
[0035] To examine salt penetration of primer film, efflorescence evaluation
was carried out
for various primers. Here, fiber cement specimens were coated on four sides
with sealer and
primer, leaving two edges (top and bottom) uncoated. After setting, each
specimen was
partially submerged in a sodium sulfate solution for 24 hours. FIG 4 shows
that back side of
specimens. In FIG. 4, there is no white precipitate visible above the point
where the sample
was submerged (arrow) for specimens primed with DC-001 and DC-002. On the
other hand,
conventional primer (C-4) showed a large amount of white precipitate
indicating sodium
sulfate above the water mark further indicating migration of salt through the
substrate and
primer film, which was visible on the primer film surface, known as
efflorescence.
[0036] A formulation for a primer as described herein has one or more of the
components
further described, which includes, generally, a binder, pigment, one or more
extenders and one
or more additives. To obtain balanced blocking resistance and wet adhesion as
well as other
performance features, formulations described herein have been optimized by
selecting
appropriate polymers as binder as well as pigments, extenders and additives.
Furthermore,
primer pigment volume concentration (PVC) was optimized to promote the balance
between
blocking resistance and wet adhesion.
[0037] Resins used herein as the binder may be therrnoplastic or thermosetting
systems.
Representative thermoplastic and thermosetting binders include acrylic
polymers, polyurethane
dispersions, epoxy emulsions, amino resin polymers, alkyds, polyesters, and
other water-based
polymer emulsions, dispersions, copolymers (including combinations thereof).
The Tg of the
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resin may be from 10 C to 90 C, from 20 C to 80 C or from 50 C to 71 C.
The polymer
emulsion/dispersion may include some volatile organic components (VOC);
however, when
desirable, the VOC will be zero. The percentage of polymers used depends on
primer PVC,
which will be discussed below.
[0038] To further improve water resistance and salt water resistance as well
as blocking
resistance, some hydrophobic polymers may be blended with the polymers
described above.
The blend dosage ma.y be from 0 to 30% or from 0.5 to 20 wt%. These
hydrophobic polymers
include siloxane, silane, fluoropolymer emulsion/dispersion, polyolefin
dispersion, as examples.
Other hydrophobic polymers known to one of skill in the art may also be used.
[0039] When polymer emulsions or latexes are used, the minimum fi1m formation
(MFT) of
the polymer emulsions may be from 0 C to 90 C, from 10 C to 80 C, or from 10 C
to 71 C.
It is desirable that polymers have a higher Tg and yet lower MFT. The larger
differences
between Tg and MFT will iinprove film forma.tion and blocking resistance.
Exatnples of such
polymers includes acrylic emulsions from DSM NeoResins (e.g., NeoCryl A6069;
a registered
trademark of DSM NeoResins, Suisweg, The Netherlands) that has a stated Tg of
56 C and
MFT at 26 C. Such emulsions or latexes may be core-shell latexes or gradient
emulsions or
latexes. For core-shell latexes or gradient latexes or emulsions, the
component may have two
Tgs with one higher and one lower. The higher one provides hardness of a final
film and the
lower one assist with film formation. To achieve an appropriate balance,
emulsions or latexes
described herein have hard core and soft shell.
[0040] When a polymer has a Tg below 50 C, certain polymers, including
siloxane wax
emulsion/dispersion and fluoropolymer dispersion may added to improve non-
blocking or
scratch resistant performance. Consideration is made to select polymers that
do not lead to
interface adhesion problems. The amount added will vary depending on actual Tg
of the
polymer used, with a balance between Tg and PVC to achieve good performance.
For
example, a polymer with high Tg may be selected if the primer PVC is
forrnulated to be lower.
[0041] To further achieve good film formation and yet a hard surface, the
resin polymer may
be a blend of hard polymers and soft polymers. The hard polymer provides non-
blocking
improvement, while a soft polymer provides good film formation. Either the
hard polymers or
soft polymers may be very hydrophobic in order to achieve good water
resistance. In such
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instances, a preferred hydrophobic polymer is a soft polymer. The ratio of
hard polymers to
soft polymer may be optimized by further evaluating good film formation after
the drying
process.
[0042] To assist film formation, plasticizers may be added. Suitable
plasticizers are known
in the art (e.g., general or functional). Examples of general plasticizers
include dibutyl
phthalate (DBP) and butyl benzyl phthalate (BBP). The amounts of a general
plasticizer may
be from 0 to 20 wt.% based on total solids content. Examples of functional
plasticizers include
alkyd dispersion/emulsion and reactive diluents. The type of alkyd
dispersion/emulsion will
often depend on curing conditions. Generally, a short oil alkyd has a short
drying time and
develops film hardness quite fast. Exainples of short oil alkyds include ones
from Cook
Composites and Polymers (e.g., Chempol 821-1391, Chempol 821-2241, Chempol
821-
1674, Chempol 824-2080; registered trademarks of Cook Composites and
Polymers, Kansas
City, MO). Reactive diluents that have low volatility, excellent thinning
properties and resin
compatible, may be added to further assist film formation without effecting
VOC. Reactive
diluents may be added into the formulation before or after drying. Exainples
of reactive
diluents include, but are not limited to di-2,7 octadienyl esters of fumaric
acid or maleic acid
and 2-(2,7-octadienoxy) succinic acid.
[0043] Particle size for the polymer emulsion or latex will often include both
large and small
sized particles. For a single polymer emulsion or dispersion, particle size
distribution may be
wide (e.g., a high solid emulsion or latex may have a bimodal distribution).
In addition, a large
particle size emulsion or dispersion may be mixed with a small particle size
emulsion or latex.
The combination of both large particle size and small particle size will
improve film packing
and formation during drying, which will improve film integrity and will also
improve high PVC
loading.
[0044] While adhesion of a primer formulation described herein may be improved
by
applying a chemical to the surface of the substrate before adding the primer
(e.g., (pretreating
the substrate to improve primer adhesion), it is also, in some embodiments,
desirable to add
one or more reactive chemicals into the primer forinulation just before
application. Such
reactive chemicals include silane, polyaziridine, carbodimide, water
dispersible isocyanate,
water dispersible epoxy, melamine, zirconium salt, and other crosslinkers.
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[0045] Hardness of a primer with non-blocking performance as disclosed herein
may be
improved with use of an encapsulated emulsion or latex. Inert pigments or
fillers, including
Ti02 and clay may also be used as a core to be encapsulated by the polymer.
Some
encapsulated anticorrosive pigments may further improve salt water resistance.
[0046] PVC of a primer formulation disclosed herein may be between about 10%
and 80%.
In several embodiments, PVC is between about 20% and 70% or between about 30%
and
70%. Typically, PVC will depend on pigments and extenders/fillers chosen, in
addition to oil
absorption and glass transition temperature of the selected polymer(s).
[0047] Pigments as disclosed herein may include organic or inorganic pigments.
Examples
of inorganic pigments include but are not limited titanium dioxide, iron
oxide, zinc oxide.
Pigments may be used in combination. The pigments selected should improve
mechanical
properties of the primer and may be anticorrosive. Examples of anticorrosive
pigments include
but are not limited to zinc phosphate, zinc polyphosphate, modified
orthophosphates, and other
phosphate related compounds. Organic pigments may include phthalocyanine blue,
phthalocyanine green, Diarylide yellow, alkali blue, Toluidine red, as
suitable examples. Some
organic pigments act as corrosion inhibitors. Organic corrosion inhibitors may
also improve
salt water resistance. Exarnples include polymeric amine salt, amino
carboxylate and organic
acid amine (e.g., Halox 520, 515 or 510; registered trademarks of the Hammond
Group or its
division, Hammond, IN). Pigments that improve both water resistance and
blocking include
zinc stearate, calcium stearate, and other stearate-related compounds. Such
pigments further
improve film forma.tion and are added at a dosage of about 5 wt.% of total
weight of the
pigment/filler.
[0048] Functional pigments/polymers may be used to improve water and salt
water
resistance. Functional pigments/polymers include ion exchange resins and ion
scavengers. Ion
exchange resins are generally crosslinked polystyrene with functional groups
and chelating
resins. The functional groups may be strongly acidic, such as sulfonic acid,
or strongly basic,
such as trimethylammonium. Weakly acidic (e.g., carboxylic acid) or weakly
basic (e.g., amino
group) functional groups may also be used. A functional pigment/polymer
includes calcium
phosphosilicate (e.g., Halox 430; registered trademarks of the Hanmmond Group
or its
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division, Hammond, IN) and zeolite. When used, functional additives are
generally in a dosage
of about 10 wt.% of the total weight of pigment/filler.
[0049] Suitable primer extenders/fillers include calcium carbonate, talc,
silica, clay, calcined
clay, wallostonite, mica, feldspar, calcium silicate, barium sulfate, zinc
oxide and any
combination thereof. In one or more embodiments, a filler includes calcium
carbonate,
calcined clay, feldspar and talc. The percentage of total pigments and
extenders used in
formulations described herein is from about 50 to about 95% of the total
weight or from about
60 to about 80%.
[0050] Additives that are used include, but are not limited to, one or more
surfactants,
dispersion agents, defoamers, leveling agents, biocides, pH adjusters,
thickeners, antiblocking
agents, coalescent agents, potassium silicate solution. The additive(s) used
will depend on
performance requirements of the formulation. Examples of surfactant/wetting
agents include
polyether modified dimethylpolysiloxane (an example of which is Byk 348, a
registered
trademark of Byk-Cera, Germany), benzyl ether, octyl phenoxy polyethoxy
ethanol,
octylphenol ethoxylate, sulfosuccinate (e.g., Triton'm CF-10, TritonTm X-10,
Triton'MX-114,
TritonTm GR-5M; trademarks of The Dow Chemical Company, Midland, MI) and
nonionic
surfactants (e.g., Surfynol7 104DPM and Surfynol7 104E, trademarks of Air
Products and
Chemicals, Inc., Lehigh Valley, PA). A hydrophilic lipophilic balance (HLB)
nonionic
surfactant may be added to iinprove shelf-life/stability, oven aging, or
resistance to freeze-thaw
cycling (e.g., ethoxylate of octyl phenol, such as TritonT" X-405, a trademark
of The Dow
Chemical Company, Midland, MI).
[0051] Suitable dispersion agents may be organic or inorganic ones, including
but not limited
to polyacid, hydrophobic copolymer polyelectrolyte (e.g., Tamol7 1254, Tamor
165A and
Tamor 681, trademarks of Rohm & Haas Company, Philadelphia, PA), block
copolymer with
pigment affinic groups (e.g., Disperbyk 190, a registered trademark of Byk-
Chemie, GmbH,
Germany) and phosphates. Suitable defoamers may be silicon based (e.g., Byk
024, Byk
019) Byk 346, registered trademarks of Byk-Cera, Germany) and/or mineral oil
based (e.g.,
Drewplus L108, Drewplus Y250, registered trademarks of Ashland Inc.,
Covington, KY)
[0052] With some formulations, biocides as preservatives, mildewcides, and/or
algicides may
be included, such as families of dioxabicyclo octane (Nuosept 95, a
registered trademark of
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WO 2009/006304 PCT/US2008/068586
ISP Investment Inc., Wilington, DE), azoniaadamantane chloride (Dowicil 75,
trademark of
The Dow Chemical Company, Midland, MI), 2-methyl-4-isothiazolin-3-one (Kathonm
LX1.5,
a trademark of Rohm & Haas Company, Philadelphia, PA). 1,2-Benzisothiazolin-3-
one
(Proxer GXL, a trademark of Arch UK Biocides Limited West Yorkshire, Uk). pH
adjusters
may be ammonium water solution, ethanol amine, trimine and ethylene diamine.
[0053] Thickeners may include conventional polymers (e.g., cellulose ether),
associative
polymers (hydrophobically modified ethylene oxide urethane, hydrophobically
modified alkali
soluble emulsion and hydrophobically modified hydroxyl ethyl cellulose),
thixotropes
(attapulgite and bentonite caly) and metal chelates.
[0054] To moderate an effect of temperature on viscosity, some other soft and
swellable
polymers may be added. The soft polymer will generally increase viscosity at
high temperature
and decrease viscosity at low temperature.
[0055] To improve blocking resistance of primers described herein, one or more
antiblocking
agents may be added, such as natural and synthetic wax dispersions, silicon
(e.g., MS-2 from
Troy Inc.) and fluoropolymer related oligomer or polymer (e.g., FS610 from
Dupont).
Aqueous solutions of ammonium may be used to adjust pH of the formulation.
Other bases,
including ethanolamine may be added to stabilize primer pH. In some
embodiments, an
emulsion latex with less carboxyl groups may be used as the primary binder to
reduce the pH
sensitivity of the formulation.
[0056] In certain embodiments, coalescent agents are incorporated into a
formulation for
better film forma.tion. Examples include ethylene glycol monobutyl ether,
diethylene glycol
monobutyl ether, ethylene glycol 2-ethylhexyl ether and 2,2,4-trimethyl-1,3-
pentanediol
monoisobutyrate. A desirable coalescent agent includes a reactive coalescent
agent that stays
inside the film and reacts with the polymer binders in the forrnulation. An
example includes a
propylene glycol monoester of corn oil fatty acids (e.g., Archer RC7, a
trademark of Archer-
Daniels-Midland Company Corporation, Decatur IL).
[0057] In one or more embodiments, a typical primer forrnulation includes up
to 60% water,
up to 1% dispersant, up to 0.5% wetting agent, up to 1% biocide, up to 1%
antiblocking
agent, up to 0.5% thickener, up to 1% ammonia water solution, up to 50%
resins, up to 30%
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WO 2009/006304 PCT/US2008/068586
pigments, up to 70% extender, and up to 1% functional pigment. TABLE 5 shows
components a typical primer formulation and acceptable ranges of the
components.
TABLE 5.
Component Example(s) Acceptable range Additional range
(wt.%) (Wt. %)
water 20 to 60 30 to 50
dispersant sodium salt of naphthalene- 0.2 to 1 0.3 to 0.6
formaldehyde condensate
wetting agent acrylic wetting agent 0.1 to 0.5 0.1 to 0.3
biocide industrial alginate 0.1 to 1 0.2 to 0.5
antiblocking agent siloxane oligomer 0.1 to 5 0.1 to 1
thickener non-ionic urethane 0.05 to 0.5 0.05 to 0.2
pH adjuster NH3H2O 0.1 to 1 0.1 to 0.5
binder latex/acrylic 5 to 80 10 to 50
pigment Ti02, Fe203 5 to 30 5 to 20
extender calcium carbonate, talc, 15 to 70 20 to 55
calcined clay, calcium
silicate
functional pigment zinc stearate 0.1 to 1 0.2 to 2
[0058] In several preferred embodiments, suitable examples of components for a
formulation
include a dispersant such as Tamol7 165, a wetting agent such as BYK 348, a
biocide such as
Nuosept 95, an antiblocking agent such as MS-2, a thickener such as 2020 NPR,
a binder
such as NeoCar 820 or NeoCar 850 (trademarks of Union Carbide Chemicals &
Plastics
Technology Corporation, Midland, MI).
[0059] The following examples provide greater detail of useful primer
forrnulations for
composite building materials, in which "part" means "part by weight" unless
otherwise
mentioned. The examples are not to be construed as limiting the scope of the
invention
described.
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WO 2009/006304 PCT/US2008/068586
[0060] For preparation of a primer forrnulation, two processes are included:
pigment paste
grinding and letdown. In the pigment paste grinding process, water, pigments,
fillers, additives
and optionally, additional polymers were mixed together and ground by Cowles
dissolver until
the particle size was about 20 to about 60 micrometers (in diameter). In a
second process,
pigment paste, polymers, water and any other additives were blended together
to form a final
formulation. Blocking, wet adhesion and salt water absorption were then
assessed after
application of the final formulation to a substrate, as described elsewhere.
[0061] Examples of representative pigment paste recipes are shown in TABLE 7.
Letdown
receipt varied with PVC used.
TABLE 6.
Example # 1 Example #2 FE-xample #3 Example #4
Water 40
Dispersant 0.84
etting agent 0.28
3iocide 0.84
Defoamer 0.18
Ti02 15 15 15 15
Si02 15
CaSiO3 30
CaCO3 20 50 48.3 21.3
Talc 15 15 10 10
Calcined clay 5 20 25 20
e2O3 yellow 0.5 0.5 0.5 0.5
e2O3 black 1.0 1.0 1.0 1.0
hthalocyanine blue 0.05 0.05 0.05 0.05
inc stearate 1.7 1.7
ticorrosive pigment 12
MP 20
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WO 2009/006304 PCT/US2008/068586
[0062] Suitable examples of select components for the above paste formulations
include a
dispersant such as TamolTm 165, a wetting agent such as BYK 348, a biocide
such as
Nuosept 95, a defoamer such as BYK 024, an anticorrosive pigment such as
Halox 430.
[0063] Example 1 of TABLE 6. The corresponding average oil absorption was
30.05. The
gravity density was 2.96. The safe PVC for non blocking was 62% for polymers
with a Tg at
500 C. Wet picking to determine wet adhesion was 55% after application to a
fiber cement
building material.
[0064] Example 2 of TABLE 6. Due to easy setting of Si02 and CaSiO3 these
components
were omitted. For non blocking, a PVC of 66% for polymers was provided with Tg
at 500 C.
Wet picking of adhesion was less than 10% after application to a fiber cement
building
material. Salt water absorption was about 26% after 8 hours of soaking when
applied to a
fiber cement building specimen.
[0065] Exainple 3 of TABLE 6. Zinc stearate was added to Example 2 to prepare
this
formulation. The safe PVC for non blocking was 66% for polymers with Tg at 50
C. Wet
picking was less than 10% when applied to a fiber cement building material.
The salt water
absorption was 13% after 8 hrs of soaking (as compared with 26% for Example 2,
which
lacked zinc stearate).
[0066] Example 4 of TABLE 6. An ion scavenger (Halox 430) and anticorrosive
pigment
(ZMP) were added to the recipe of Example 3. The salt water absorption was
reduced to
about 10%. Wet picking was 50% for safe non blocking PVC of 66% for polymers
with Tg at
50 C.
[0067] Exatnple 5 of TABLE 6. To a recipe of Example 3, NeoCryl A639
(trademark of
DSM IP Assets B.V., The Netherlands) was used as the binder. It had a Tg at 62
C and
MFT at 53 C. PVC was from 10 to 80% for non blocking performance. A preferred
PVC
was between about 10% to 65% for both a non blocking and wet picking of zero.
[0068] When coating a composite building material with a primer forrnulation
described
herein, the coating may be applied by methods known in the art, including
brushing, spraying,
dabbing, and all forms in between. The primer formulation may be applied to a
cured or
uncured composite building material that is sealed or unsealed. The primer
forinulation may be
applied to all or a portion of the exposed surface of the composite building
material. In one
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WO 2009/006304 PCT/US2008/068586
representative example, the primer formulation is applied to unsealed fiber
cement building
materials. In a first embodiment, the fiber cement building materials were
uncured. In a
second embodiment, the fiber cement building materials were at least partially
cured. The
primer formulation was applied at a thickness less than 1 mil, preferably less
than 0.8 mil,
preferably between about 0.25 mil and 0.6 mil. Relative thickness will depend
on the material
and its use. The thickness may be achieved in a single coat or may be reached
by additional
consecutive coats. After application of the primer formulation to the desired
thickness, the
fiber cement building material is cured. Curing is preferably in oven an oven
with an exit board
surface temperature of at or about 150 degrees Fahrenheit or greater. As such,
described
herein is a composite building material coated with at least one layer of a
primer forrnulation as
evidenced in TABLES 5-6, in which the composite building material may be cured
or uncured,
sealed or unsealed, and the primer formulation as described herein is applied
to a thickness of
1.0 mil or less, wherein the coated composite building material is then cured.
[0069] Embodiments of the primer described herein provided certain improved
physical and
chemical properties as compared with an alternative primer. In some
embodiments, a primer
has improved moisture absorption characteristics. In a preferred
implementation, a primer
formulation as described herein when provided to a composite building material
promotes a
reduction in moisture absorption of about 25%, more preferably about 50%, more
preferably
about 75% as compared to an equivalent coating of a different primer.
[0070] A primer as described herein also provides a composite building
material with
improved adhesion to paint and other exterior coatings such that the peel
failure is reduced
from about a 70%-90% failure rate to better than about 50%, more preferably
better than
about 25%, more preferably better than a near 0% failure rate.
[0071] While primers for composite building materials, such as cementitious
materials, are
available, alternate, conventional primers are not adequate and have poor
performance with
composite building materials (e.g., materials that are generally cementitious,
gypsum, or of
another inorganic building material, such as those containing cellulose,
glass, steel or polymeric
fibers). Additionally, some alternate, conventional primers typically have a
high viscosity, form
a film on the surface of the building material and do not effectively block
moisture from
penetrating the composite building material. Consequently, paint adhesion and
long term paint
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durability on these composites are less than optimal. As described herein is a
primer that
overcomes these and other problems when applied to a composite building
material and acts as
a weather-guard or hydrophobic treatment to all surfaces of the composite
building material.
[0072] Also described is a method of forming at least one layer of a primer
formulation on an
article comprising the steps of applying a first layer to a substrate, the
first layer comprising a
primer formulation, and applying a second layer on the first, wherein the
second layer is a
topcoat.
[0073] In still additional embodiments, a primer disclosed herein, when
applied to a
composite building material, improves adhesion between the composite material
and a sealer
and/or paint.
[00741 Embodiments described herein advantageously provide composite building
materials
with one or more desirable characteristics, such as reduced water absorption,
reduced rate of
water absorption, lower water migration, and lower water permeability,
enhanced wet and dry
adhesion, improved stack damage resistance, improved freeze-thaw resistance
(e.g., in water
or in solutions comprising a soluble salt), chemical resistance, resistance to
soluble salt ingress,
and better mechanical properties as compared to materials absent embodiments
described
herein or as compared with building materials comprising alternative or
conventional primers.
[0075] In addition, described herein is application of a primer formulation
described to a
composite building material, wherein application includes coating a primer
forrnulation to a
composite building material, such as a fiber cement material, to a thickness
of 1.0 mil or less,
wherein the composite building material is uncured or partially cured and then
cured after
coating. Curing preferably includes baking at a temperature greater than 150
or 160 F until
the coated composite has surface temperature greater than 150 or 160 F.
[0076] Still further, described herein is an iinproved primer formulation for
the improved
adhesion of a topcoat to a composite building materials, wherein the
improvement is a
reduction in a peel failure of the topcoat by greater than 50% as compared to
a primer of a
same thickness and a different formulation.
[0077] An improved primer formulation for the improved performance of a
composite
building materials is also described herein, wherein the improvement is a
reduction in moisture
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absorption of about 25% as compared to a primer of a same thickness and a
different
formulation.
[0078] A composite building material with an improved primer formulation
applied to its
surface is described herein, wherein the improved primer formulation reduces
moisture
absorption of the composite building material by at least 25% as compared to a
primer
formulation of a same thickness and a different formulation.
[0079] In a process for priming a fiber cement building product, the process
may comprise
the step of coating a fiber cement building product with an improved primer
formulation as
described herein.
[0080] Although the foregoing description of the preferred embodiments has
shown,
described and pointed out certain novel features of the invention, it will be
understood that
various omissions, substitutions, and changes in the form of the detail as
illustrated as well as
the uses thereof, may be made by those skilled in the art, without departing
from the scope of
the invention. Particularly, it will be appreciated that the preferred
embodiments may manifest
itself in other shapes and configurations as appropriate for the end use of
the article made
thereby.
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